Single-bath chrome dyeing processes and compositions, including ammonium sulfate and diammonium phosphate



April 22, 1952 w. B. COLEMAN ETAL 2,593,850

SINGLE-BATH CHROME DYEING PROCESSES AND COMPOSITIONS, INCLUDING AMMONIUM SULFATE AND DIAMMONIUM PHOSPHATE Filed Oct. 8, 1949 Patented Apr. 22, 1952 SINGLE-BATH CHROME DYEING PROCESSES AND COMPOSITIONS, INCLUDING AlVIlVIO- NIUM SULFATE AND DIAMMONIUM PHOS- PHATE William B. Coleman, Crete, Ill., and Gerald M. Cot, Wellesley, Mass., assignors to Victor Chemical Works, a corporation of Illinois Application October 8, 1949, Serial No. 120,384

11 Claims. (C1. 8-30) This invention relates to an improvement in chrome dyeing and compositions Afor use therein.

Chrome dyeing has conventionally been carried out in baths containing Glaubers salt and ammonium sulfate, in addition to the chromate salt and the dye. In the treatment of wool with such baths, the practice has been to prepare a slightly alkaline bath in which the wool is immersed for a suicient time to swell the fibres and permit penetration by the dyestuiis. Without such alkaline soaking, dyeing occurs merely on the surface. After the alkaline treatment it has been the practice to add successive. additions of such acids as formic, acetic, sulfuric and phosphoric to increase the acidity and lower the pH. During this acidication, according to present theories, the wool first reacts with the acid, the acidic wool then combines with the dye, and the dyed wool reacts with the chrome mordant to x the dye on the wool as an insoluble complex. Metachroine dyeing is a procedure in which both the dye and the chrome mordant are initial components of the dye bath, and the dyeing is controlled by addition of acids at the critical stages of the process.

Normally the application of heat accelerates the dyeing process so that it is conventional to boil the liquid in the bath.

In order to obtain a completely satisfactory chrome dyeing of woolen materials, it is essential that the pH of the'bath be very closely controlled. T he increase in acidity must be gradual, otherwise, the dye Will suddenly deposit upon the fabric, l

and great unevenness of dyeing will result. Such unevenness is known as unlevelness and "skitteriness in the trade, and is a result of the characteristics of the bres and a sudden.change in pH of the dyebath. A inal pH of 5.2 to 5.8 is desired to fully develop and x the color.

The control of the acidity of the dye bath by addition of acid has several considerable disadvantages. Perhaps the most important is the fact that the bath mustbe cooled before the lacid is added. After this the bath is reheated. This results in a .very considerable loss-ottime, as well as the cost of the heating operation. Secondly, it is quite diincult to control the acidity throughout the solution, particularly since any addition of acid must be made more or less locally, with the result that the pH in that locality is reduced below the general average. Therefore, unlevelness and skitteriness are common.

We have discovered that a chrome dyeing bath may be prepared having an initial pH Within the desirable range of alkalinity which, by the application of heat may be converted at the desired rate to a bath having an acid pH which will maintain itself automatically in the desired range. Be,

cause the change in pH comes from inside the bath, rather than from outside additions, the change can be made with absolute uniformity.

These results may be accomplished by the addition to the bath of suitable proportions of diammonium phosphate, or a mixture of diammonium phosphate with one or more ammonium salts of a strong acid, and particularly ammonium sulfate. The initial pH of such a bath is slightly alkaline, but after the bath is heated to boiling, the diammoniurn phosphate slowly decomposes, resulting in a gradual increase in the acidity of the solution and a gradual deposition of dyestu upon the libres. The decomposition of diammonium phosphate proceeds until equilibrium conditions are reached at a pH of 6.2 to 6.5. When diammonium phosphate by itself is used as a buffering agent, the final pH attainedl by the chrome bath will not drop to below 6.2. Certain colors are developed in a bath of that acidity; however, `for other colors an end pH of 5.2 to 5.8 is desirableV for full development of the dye. Consequently when a pH of about 6.2 is reached in the dye bath, formic, phosphoric, sulfuric or acetic acid may be added to reduce the iinal pH to thedesired Value of 5.2 to 5.8, and the dyeing operation completed at that acidity.

The addition of an ammonium salt of a strong acid, as ammonium sulfate, together with diammonium phosphate to a metachrome dye bath, depending upon proportions used, will result in a bath that is initially alkaline, but upon boiling together with the material to be dyed, will attain the desired pH of 5.2 to 5.8 without the addition of acid. Ammonium sulfate itself does not give the initial alkalinity, and it is added for reasons of producing a final acidity greater than that of diainmonium phosphate when used alone. W oolen materials dyed by use of such a bath have resulted in good bath exhaustion, 'level and full development of bright and fast colors, whereas when a standard metachrome dye bath and methods known to prior art were used, uneven dyeing of cloth was often obtained.

For comparative purposes two chrome dyeing tests were made using: (A) a standard metachrome dye bath of the formula- 2% Chromate Brown EBC dye Glaubers salt 3% Ammonium sulfate 1% Neutral sodium chromate and, (B) a similar bath in which the 3% ammonium sulfate was replaced with 3% diammonium phosphate. In both cases the percentages are based on the weight of goods to be dyed. The ratio of water to goods was 30 to 1 in both cases. The goods tested were strips of a piece of wool cloth which had been previously carbonized in a dilute sulfuric acid bath in accordance with standard commercial practice. The cloth, joined in the form of a continuous belt, was immersed in the dye bath and slowly turned to achieve even wetting of the cloth. The bath was brought to a boil in one hour, and then where several adjustments in the pH of the bath are necessary to obtain satisfactory results.

By the substitution of ammonium sulfate for the Glaubers salt of the prior art, and the simultaneous use of diammonium phosphate, it has been possible to control the pH of the dye bath from the slight alkalinity required at the start to the low pH of 5.2 to 5.8 desired at the end of the process for fixing the dye, such control being obtained without intermediate adjustments or acid additions;

By use of such new combination of assistants we have found that the dye, mordant and assistants can be employed in a single bath to give an efficient, satisfactory and substantially foolproof one-step process for the chrome dyeing of wool.

In some cases it may be desirable to adjust the initial pH value of the bath, depending on the nature of the wool to be dyed. For example, the bath may be adjusted with ammonia to offset the acidity of some types of wool, especially those which have had an acid pretreatment.

The one-step dye bath of the present invention should include a predetermined amount of the desired chrome dye with sufficient sodium or ammonium chromate or dichromate to act as a mordant, ammonium sulfate and diammonium phosphate dissolved in Water to give a solution of the desired concentration.

TWO metachrome dye baths illustrating the invention were made up in the following proportions:

boiled for an additional forty-five minutes. Two I H percent (2%) (on weight of cloth) of 28% acetic acid was then added, and the bath boiled an adper m Per em ditlonal half hour, Chrome Fast Blue BX Conc 1. 0 1.0

7 The following table shows the pH values of the flusph *gjg Sgjg bath at intervals during the operation of the 40 Sodlum dwhwmate 1.70 1.0 process:

Bath bafore Bath after Start of boil Acid addition contact vvith contact fvith M15 M36 M40 K W00 W00 1 lllS KUS. lIlS.

' f 6o 70 9o 105 12o 135 Room mmp- Room temp' Mins. Mins. Mins. Mins. Mins. Mins.

A. Ammonium sulfate 7.0 6.6 5.2 5.7 6.2 6.4 6.4 6.4 6.4 5.1 5.1 B. Diamnionnmi phosphate 7. 7 7. 4 7. 1 7. l 7. 1 7. 1 6. 7 6. 7 6. 7 5. 4 5. 4

The inuence of the wool acidity can be clearly where percentages refer to Weight of wool. The

seen not only at the moment of contact with the bath, but at succeeding intervals as Well. The relative stabilities of the solutions toward change are also evident. VIt, will be seen that the standard dye bath formula has little buffering power, whereas the dye bath containing the diammonium phosphate had excellent buffering power. The initial development of acidity in (A) resulted in rapid deposition of the dye on the cloth before a uniform distribution of the dye could take place, whereas the much longer period of alkalinity control in (B) permitted the uniform distribution of dye throughout the cloth before the acidity was increased sufficiently to cause deposition of the dye. The results were that the cloth of test (A) was dyed unevenly, and that of (B) was uniform and highly satisfactory.

As illustrated in the above example (B), the use of a single addition of acid at the end of the boiling period to reduce the final pH gives satisfactory results. This represents an improvement over prior chrome dyeing procedures baths were diluted with thirty parts of water per part of cloth. Test dyeings were carried out These two compositions gradually reach the desired final pH. The initial pH Vcan be easily adjusted to alkalinity by addition of ammonium chosen in the above examples because it is a dye dium dichromate and ammonium chromate.`

When ammonium chromate was used as the mordant, it was possible to reduce the amount of ammonium sulfate necessary to produce the desired final pH value. However, sodium chromates are preferred because of their commercial availability.

Considerable variation in the Vamounts and proportions of the assistant compounds is possible without detrimental eect in the dyebath. In general, the proportions are selected to provide a buffered pH range from about 7.5 down to `about 5.2. In all cases the pI-I of the bath will be affected by the type of water used and the condition of the wool; i. e., if the water is hard or soft,

and whether the wool is neutral, basicor acidic. Tomeet conditions that are often encountered in commercial dyeings, such as the necessity of using hard water and/or the use of not completely neutralized wool, it has been found that from 15 to 30% ammonium sulfate, and from 1 to 9% diammonium phosphate with 1 to 3% sodium dichromate (or sodium or ammonium chromates) based on the weight of the wool, will give entirely satisfactory results when employed with 1 to 3% of a chrome dye selected from the class of dyes classified in the A. A. T. C. C. Technical Manual and Year Book of 1947-1943 as Mordant Acid dyes, which dyes are capable of forming metalliccomplexes with a metallic salt, for example, sodium dichromate. When more ideal conditions for dyeing are present, such as soft Water and a completely neutralized wool, the amount of ammonium sulfatemay be' considerably reduced. In such cases good pH control and successful Vdyeings have been effected with the use of but 10% ammonium sulfate. i

It is preferred to prepare the new dye assistant composition as a dry solid material whichmay be added to the dye bath in 'the desired concentration, together with the dye selected to givethe required color and shade. The function of the mordant compound is that of forming a metal complex with the dye to fix the dye on the woolv fibers. The amount of mordant is more or less dependent on the amount of dye employed. and the amount of wool being processed, and has no critical relationship to the amounts of ammonium sulfate and diammonium phosphate inthe solution or dry composition. In general, `the amount of mordant compound should be within the range of 1 to 3% based on theffweight of wool tobe dyed. The functions ofthe ammonium sul-' fate and fdiammonium phosphate are dependent on each other,.and the `combination effect is that of buffering thesolution over wide range of pH control. In ,general the higher the proportion of ammonium sulfate, the lower the pH obtained may be controlled, provided sufficient diammonium phosphate ispresent to buffer the solution in the higher pH range and control the rate of lowering the pH. We have found that a range of 15 to 30% ammonium sulfate and 1 to 9% of diammonium phosphate, based on the weight of wool, is sufncient for satisfactory pH control of the dye bath. Based on these proportions, a solid composition within the range of 96.7-62.5% ammonium sulfate and from 3.3-37.5% diammonium phosphate will give satisfactory pH controlwhen dissolved in the dye bath. i.

The drawing is a triaxial diagram illustrating the preferred limits of the three element solid composition. As is well known, the proportion of each ingredient is indicated by that percentage of the distance from the base opposite the indicated point for that compound, to that point. Thus the line AB on the diagram is 93.8% from the base of the triangle to the peak marked 100% ammonium sulfate, and, therefore, indicates 93.8% ammonium sulfate in the composition. The line BC is 21/2% of the distance from the base to which it is parallel to the lower lefthand corner representing 100% mordant salt, and therefore indicates 21/2% of that material.

The three component solid composition may be made up by mixing the three components in the percentage proportions represented within the area bounded by the lines AB, BC, CD, DE, EF and FA of the triaxial diagram, wherein lines AB and DE define maximum and minimum ani-cunts of ammonium sulfate; lines EF and BC denne maximum and minimum amounts of `mordant salt; and the lines CD and FA define maximum and minimum amounts of diammonium phosphate. The maximum and minimum amounts of each component are represented by the percentage figures: 93.8-55.6% for ammonium sulfate, 36.0*3.0% for diammonium phosphate and 15S-2.5% for the mordant salt.

Compositions within the indicated area of the diagram may vary somewhat in their pI-I control characteristics, but all are capable of effecting a satisfactory control of the dye bath within the pH range of about 7.5 down to about 5.2 during the boiling operation.

Some` variation may be encountered in the utilization of such compositions due to the differ? ent acidities of the various mordant compounds. It is, therefore, desirable, in addition to the lirni-i tations already prescribed for these compounds, to correlate the proportions of the ingredients so that the resulting compound will producea lpI-I from approximately 6.9 to v7.5 when dissolved'in a 1% solution in water. However, as pointed out, if the pH is too low, it may readily be adjusted by the addition of a very small amount of ammonium hydroxide.

The ysolid compositions represented above may be dissolved in water in concentrations suitable for the dyeing operation. VWe have foundithat.

based on the preferred use of 15 to 30 pounds of ammonium sulfate per 100 pounds of wool, the abovevassistant compositions may be dissolved in 2000' to 4000 pounds of water, preferably 3000 poundslof water. This means an ammonium sulfate `concentration of from 0.375% to 1.5%, preferably from 0.5% to 1.0%. Thus, the solid assistant compositions'may be used the dye bath on the'b'asis ofl an ammonium sulfate concentration of 0.37 to.1.5% for satisfactory dyeing operations.

As further examples of the invention, dyeings were made using various concentrations and proportions as shown in the following table:

36.0 parts by Weight of diammonium phosphate, and 2.5 to 15.8 parts by Weight of the mordant compound, and which when dissolved in a 1% Assistant Composition C D E F G Dry basis:

Ammonium Sulfate pcrcent 55. 5 62. 5 83. 3 81.1 90.0 Diammonium Phosphate -..do,. 33. 3 31. 3 12. 5 13. 5 6. 25 Sodium Dichromate do.. 11.2 6.2 4. 2 5. 4 3. 75

T0151 .do.. 100.0 100.0 100.0 100.0 100.0 Bath-Pounds per 100 pounds of Wmonium suimte 15.0 10.0 20.0 30.0 24.0 Diammoniuni phosphate 9.0 5. 3.0 5. 0 l. 66 Sodium Dichromate 3.0 1. 0 1.0 2. 0 1. 0 Water s, 000.0 3, 000.0 3,000.0 3,000.0 3,000.0 Dye 1.0 1.0 1.0 1.0 1.0 initial pH of bath 7. 0 7. 3 7.1 1 0. 0 0. 7 pH after adding wool 6.8 7.0 6.95 7. 5 6. 6 After heating min, at 180 F 6. 6 6.6 6.7 7. 0 6. 5 min 0. 3 0. 5 e. 4 0. 5 5. s 0.2 0.5 6.15 0.2 6.0 s. 05 0.1 5.0 0.0 5.9 5.0 0.0 5.9 5.9 5. 75 5.5 5.9 5.8 5.75 5.0 5. 75 5. 55 5.7 5. e5 5.0 5.7 5.5 v5.7 5.0 5.5 5.0 5.8 5.0 5.5 5.5 5.5 5.8 5.0 5.5 5.5

l Adjusted to 7 .8 with NH4OH.

Dyeing results obtained in examples C, D, E and aqueous solution has an initial pH of 6.9 to 7.5 F were excellent. Those obtained in example G before heating. were good. 3. A composition Ias set forth in claim 1 in Example G, while still illustrating an operable 30 which the mordant is sodium dichromate. procedure, is not so satisfactory as examples C, D, 4. A dye bath comprising an aqueous solution E and F because of the lower buffering capacity including a chrome mordant acid dye, ammonium at the start of the dyeing operation. sulfate, dammonium phosphate and a chromium The solid assistant compositions may also inmordant compound selected from the group conclude the chrome dyestuff if desired, but it is presisting of sodium chromate, sodium dichromate, ferred not to include the dye in order to permit ammonium chromate and ammonium dichrothe dye bath operator to standardize on the asmate, wherein the components other than Water sistant composition and vary only the dyestui are selected within the percentage range of 55.6 to obtain the desired colors and shades. to 93.8 parts by weight of ammonium sulfate, 3.0

While the above assistant compositions OTer 40 to 36.0 parts by weight of diammonium phosa simple and trouble proof means of controlling phage, and 2.5 to 15.8 parts by Weight of the the dyeing operation, it is sometimes desirable, mordant compound. as in "top chrome dyelng. to add the mordant 5. A dye bath as set forth in claim 4 in which Salt at a late Stage of the dyelng 013010191011. Dyethe mordant is sodium dichromate. ins vperatlons 0f this type may be Carried Outby 15 c. A dye bath as ser forth in claim 4 in which employing an assistant composition containing the Concentration of ammonium sulfate in the the ammmPum Sulfate and dlamfflfmum Phosaqueous solution is from 0.37 to 1.5% by weight. phate addmg he 'flyestuffhand bollmg upm the 7. A dye bath assistant composition comprising gllieantpltva ue 1S Teac ed' then addmg the 50 amixture of ammonium sulfate and diaminonium phosphate, the proportions being within the range ...111.25553555531155esta.tdas of t@ by of ammonium sary limitations should be understood therefrom, frind 37'5 to 3'3 parts by Welght of dlam' In phosphate. as modifications will be obvious to those skilled in the art r5 8. A dye bath composition comprising an aque- We canr 0 ous solution containing approximately. 1% by 1. A dye bath assistant composition consisting Wlghloemgnoumdsmfat?, 17% dlammomlm of ammonium sulfate, diammonium phosphate p* Osp a o /0 S01 mm dm Tomate andasult' and a chromium mordant compound selected able amount of a' Cl'fome morda1-t-ac1d dyfrom the group consisting of sodium chromate, 9' A dy? bath asslstant Composmon @Qnslstmg sodium dichromate, ammonium chiomate and 0f 'approxlmately 83% by weight ammonium sul-` ammonium dichromate, wherein the components faltfj' 14% @ammonium Phosphate and 3% 0f are selected within the percentage range of 55.6 sodlum dlchromatef to 93.8 parts by weight ammonium sulfate, 3.0 to .10- `he PTQCGSS 0f 05'01115 WOOl which 00m'- ,36.0 parts by weight of diammonium phosphate, p1`1ses-11-nmefsmg Said V001 in an aqueous bath and 2.5 to 15.8 parts by weight of the mordant Contalnmg, Der 100 130111105 0f WOOL flOm 1 150 3 Compound Y pounds of a chrome dye, from 15 to 30 pounds of 2. A dye bath assistant composition consisting ammonium sulfate, from 1 to 9 poundsv of diof ammonium sulfate, diammonium phosphate ammOIlllm phOSphate, and 1 to 3 pounds of a and a chromium mordant compound selected mord-ant compound selected from the group confrom the group consisting of sodium chromate, sstng of sodium chromate, sodium dichromate, sodium diehromate, ammonium chromate and ammonium chromate and ammonium dichroammonium dichromate, wherein the components mate, and heating the bath at a temperature of are selected Within the percentage range of'5516 180 F. to boiling for a suicient period to effect to 93.8 parts by weight ammonium sulfate, 3.0 to

automatic lowering of the pH value to within the range of pH 5.2 to 5.8 without the addition of an acid. i

11. The process of dyeing wool which comprises immersing said Wool in an aqueous bath containing, per 100 pounds of Wool, from 1 to 3 pounds of a chrome dye, from 15 to 30 pounds of ammoniumsulfate, from 1 to 9 pounds of diammonium phosphate, and 1 to 3 pounds of a mordant compound selected from the group consisting of sodium chromate, sodium dichromate, ammonium chromate and ammonium dichromate,

and heating the bath at a temperature of 180 F.

to boiling fora sufficient period to eTect automatic lowering of the pH value to within the range of pH 5.2 to 5.8 without the addition of an acid, said bath containing sucient water to give I0 a bath weighing from 20 to 40 times the weight of the Wool.

WILLAM B. COLEMAN. GERALD M. COT.

REFERENCES CITED The following references are oi' record in the le of this patent:

Bleaching Dyeing and Chemical Technology of Textile Fibers, by Trotman and Trotman, 2nd edition, 1946, Grifn and Company, Ltd., London; pages 362 and 363.

Amer. Dyestuf Reporter for August 23, 1948, pages P547, P548.

Journal Soc. Dyers and Col. for December 1945, pages 328 to 333. 

1. A DYE BATH ASSISTANT COMPOSITION CONSISTING OF AMMONIUM SULFATE, DIAMMONIUM PHOSHPATE AND A CHROMIUM MORDANT COMPOUND SELECTED FROM THE GROUP CONSISTING OF SODIUM CHROMATE, SODIUM DICHROMATE, AMMONIUM CHROMATE AND AMMONIUM DICHROMATE, WHEREIN THE COMPONENTS ARE SELECTED WITHIN THE PERCENTAGE RANGE OF 55.6 TO 93.8 PARTS BY WEIGHT AMMONIUM SULFATE, 3.0 TO 36.0 PARTS BY WEIGHT OF DIAMMONIUM PHOSPHATE, AND 2,5 TO 15.8 PARTS BY WEIGHT OF THE MORDANT COMPOUND. 